Custom HTTP Clients for the Twilio Java Helper Library

If you are working with the Twilio Java Helper Library, and you need to be able to modify the HTTP requests that the library makes to the Twilio servers, you’re in the right place. The most common need to alter the HTTP request is to connect and authenticate with an enterprise’s proxy server. We’ll provide sample code that you can drop right into your app to handle this use case.

Connect and authenticate with a proxy server

To connect and provide credentials to a proxy server that may be between your app and Twilio, you need a way to modify the HTTP requests that the Twilio helper library makes on your behalf to invoke the Twilio REST API.

The Twilio Java helper library uses the HttpClient interface (in the org.apache.http.client package) under the hood to make the HTTP requests. With this in mind, the following two facts should help us arrive at the solution:

1. Connecting to a proxy server with HttpClient is a solved problem.
2. The Twilio Helper Library allows you to provide your own HttpClient for making API requests.

So the question becomes: how do we apply this to a typical Twilio REST API example?

Twilio.init(ACCOUNT_SID, AUTH_TOKEN);

Message message = Message.creator(new PhoneNumber("+15558675310"),
        new PhoneNumber("+15017122661"), "Hey there!").create();

Where is TwilioRestClient created and used? Out of the box, the helper library creates a default TwilioRestClient for you, using the Twilio credentials you pass to the init method. However, nothing is stopping you from creating your own and using that.

Once you have your own TwilioRestClient, you can pass it to any Twilio REST API resource action you want. Here’s an example of sending an SMS message with a custom client:

Create your custom TwilioRestClient

When you take a closer look at the constructor for TwilioRestClient, you see that the httpClient parameter is actually of type com.twilio.http.HttpClient.

HttpClient is an abstraction that allows plugging in any implementation of an HTTP client you want (or even creating a mocking layer for unit testing).

However, within the helper library, there is an implementation of com.twilio.http.HttpClient called NetworkHttpClient. This class wraps the org.apache.http.client.HttpClient and provides it to the Twilio helper library to make the necessary HTTP requests.

Call Twilio through the proxy server

Now that we understand how all the components fit together, we can create our own TwilioRestClient that can connect through a proxy server. To make this reusable, here’s a class that you can use to create this TwilioRestClient whenever you need one:

In this example, we use some environmental variables loaded at the program startup to retrieve various configuration settings:

• Your Twilio Account Sid and Auth Token (found here, in the Twilio console)
• Your proxy server host
• Your proxy port

These settings are located in a file named .env like so:

ACCOUNT_SID=ACxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
AUTH_TOKEN= your_auth_token

PROXY_HOST=127.0.0.1
PROXY_PORT=8888

Here’s a console program that sends a text message and shows how it all can work together. It loads the .env file for us.

What else can this technique be used for?

Now that you know how to inject your own HttpClient into the Twilio API request pipeline, you could use this technique to add custom HTTP headers and authorization to the requests, perhaps as required by an upstream proxy server.

You could also implement your own HttpClient to mock the Twilio API responses so your unit and integration tests can run quickly without needing to make a connection to Twilio.

We can’t wait to see what you build!